Stress-induced nuclear condensation of NELF drives transcriptional downregulation.

In response to stress, human cells coordinately downregulate transcription and translation of housekeeping genes. To downregulate transcription, the negative elongation factor (NELF) is recruited to gene promoters impairing RNA polymerase II elongation. Here we report that NELF rapidly forms nuclear condensates upon stress in human cells. Condensate formation requires NELF dephosphorylation and SUMOylation induced by stress. The intrinsically disordered region (IDR) in NELFA is necessary for nuclear NELF condensation and can be functionally replaced by the IDR of FUS or EWSR1 protein. We find that biomolecular condensation facilitates enhanced recruitment of NELF to promoters upon stress to drive transcriptional downregulation. Importantly, NELF condensation is required for cellular viability under stressful conditions. We propose that stress-induced NELF condensates reported here are nuclear counterparts of cytosolic stress granules. These two stress-inducible condensates may drive the coordinated downregulation of transcription and translation, likely forming a critical node of the stress survival strategy.

Effective management of recurrent Doege-Potter syndrome with somatostatin-analogues: A case report.

BACKGROUND: Doege-Potter syndrome is defined as paraneoplastic hypoinsulinemic hypoglycemia associated with a benign or malignant solitary fibrous tumor frequently located in pleural, but also extrapleural sites. Hypoglycemia can be attributed to paraneoplastic secretion of "Big-IGF-II," a precursor of Insulin-like growth factor-II. This prohormone aberrantly binds to and activates insulin receptors, with consecutive initiation of common insulin actions such as inhibition of gluconeogenesis, activation of glycolysis and stimulation of cellular glucose uptake culminating in recurrent tumor-induced hypoglycemic episodes. Complete tumor resection or debulking surgery is considered the most promising treatment for DPS. CASE: Here, we report a rare case of a recurrent Doege-Poter Syndrome with atypical gelatinous tumor lesions of the lung, pleura and pericardial fat tissue in an 87-year-old woman. Although previously described as ineffective, we propose that adjuvant treatment with Octreotide in conjunction with intravenous glucose helped to maintain tolerable blood glucose levels before tumor resection. The somatostatin-analogue Lanreotide was successfully used after tumor debulking surgery (R2-resection) to maintain adequate blood glucose control. CONCLUSION: We conclude that somatostatin-analogues bear the potential of being effective in conjunction with limited surgical approaches for the treatment of hypoglycemia in recurrent or non-totally resectable SFT entities underlying DPS.

Multiomic spatial landscape of innate immune cells at human central nervous system borders.

The innate immune compartment of the human central nervous system (CNS) is highly diverse and includes several immune-cell populations such as macrophages that are frequent in the brain parenchyma (microglia) and less numerous at the brain interfaces as CNS-associated macrophages (CAMs). Due to their scantiness and particular location, little is known about the presence of temporally and spatially restricted CAM subclasses during development, health and perturbation. Here we combined single-cell RNA sequencing, time-of-flight mass cytometry and single-cell spatial transcriptomics with fate mapping and advanced immunohistochemistry to comprehensively characterize the immune system at human CNS interfaces with over 356,000 analyzed transcriptomes from 102 individuals. We also provide a comprehensive analysis of resident and engrafted myeloid cells in the brains of 15 individuals with peripheral blood stem cell transplantation, revealing compartment-specific engraftment rates across different CNS interfaces. Integrated multiomic and high-resolution spatial transcriptome analysis of anatomically dissected glioblastoma samples shows regionally distinct myeloid cell-type distributions driven by hypoxia. Notably, the glioblastoma-associated hypoxia response was distinct from the physiological hypoxia response in fetal microglia and CAMs. Our results highlight myeloid diversity at the interfaces of the human CNS with the periphery and provide insights into the complexities of the human brain's immune system.

Transcriptome Analysis Identifies Accumulation of Natural Killer Cells with Enhanced Lymphotoxin-ß Expression during Glioblastoma Progression.

Glioblastomas are the most common primary brain tumors. Despite extensive clinical and molecular insights into these tumors, the prognosis remains dismal. While targeted immunotherapies have shown remarkable success across different non-brain tumor entities, they failed to show efficacy in glioblastomas. These failures prompted the field to reassess the idiosyncrasies of the glioblastoma microenvironment. Several high-dimensional single-cell RNA sequencing studies generated remarkable findings about glioblastoma-associated immune cells. To build on the collective strength of these studies, we integrated several murine and human datasets that profiled glioblastoma-associated immune cells at different time points. We integrated these datasets and utilized state-of-the-art algorithms to investigate them in a hypothesis-free, purely exploratory approach. We identified a robust accumulation of a natural killer cell subset that was characterized by a downregulation of activation-associated genes with a concomitant upregulation of apoptosis genes. In both species, we found a robust upregulation of the Lymphotoxin-ß gene, a cytokine from the TNF superfamily and a key factor for the development of adaptive immunity. Further validation analyses uncovered a correlation of lymphotoxin signaling with mesenchymal-like glioblastoma regions in situ and in TCGA and CGGA glioblastoma cohorts. In summary, we identify lymphotoxin signaling as a potential therapeutic target in glioblastoma-associated natural killer cells.

Nascent-protein ubiquitination is required for heat shock-induced gene downregulation in human cells.

Proteotoxic stress such as heat shock causes heat-shock factor (HSF)-dependent transcriptional upregulation of chaperones. Heat shock also leads to a rapid and reversible downregulation of many genes, a process we term stress-induced transcriptional attenuation (SITA). The mechanism underlying this conserved phenomenon is unknown. Here we report that enhanced recruitment of negative transcription elongation factors to gene promoters in human cell lines induces SITA. A chemical inhibitor screen showed that active translation and protein ubiquitination are required for the response. We further find that proteins translated during heat shock are subjected to ubiquitination and that p38 kinase signaling connects cytosolic translation with gene downregulation. Notably, brain samples of subjects with Huntington's disease also show transcriptional attenuation, which is recapitulated in cellular models of protein aggregation similar to heat shock. Thus our work identifies an HSF-independent mechanism that links nascent-protein ubiquitination to transcriptional downregulation during heat shock, with potential ramifications in neurodegenerative diseases.

Heat-Shock Protein 90 Controls the Expression of Cell-Cycle Genes by Stabilizing Metazoan-Specific Host-Cell Factor HCFC1.

Molecular chaperones such as heat-shock proteins (HSPs) help in protein folding. Their function in the cytosol has been well studied. Notably, chaperones are also present in the nucleus, a compartment where proteins enter after completing de novo folding in the cytosol, and this raises an important question about chaperone function in the nucleus. We performed a systematic analysis of the nuclear pool of heat-shock protein 90. Three orthogonal and independent analyses led us to the core functional interactome of HSP90. Computational and biochemical analyses identify host cell factor C1 (HCFC1) as a transcriptional regulator that depends on HSP90 for its stability. HSP90 was required to maintain the expression of HCFC1-targeted cell-cycle genes. The regulatory nexus between HSP90 and the HCFC1 module identified in this study sheds light on the relevance of chaperones in the transcription of cell-cycle genes. Our study also suggests a therapeutic avenue of combining chaperone and transcription inhibitors for cancer treatment.